Electron irradiation process

ABSTRACT

A METHOD FOR PRODUCING A MULTIPLE-COLOR SOAP BAR BY DIRECTING HIGH ENERGY ELECTRONS TOWARD A SURFACE OF A SOAP BAR, INTERPOSITIONING, BETWEEN THE BAR SURFACE AND THE ELECTRON SOURCE, A SHIELD HAVING A DESIGN THEREIN, AND CAUSING THE DESIGN CONFIGURATION TO BE APPLIED TO THE SOAP BAR BY COLORATION OR A CHANGE IN COLOR OF THE PORTION OF THE BAR EXPOSED TO THE ELECTRON RADIATION; AND THE MODIFICATION OF SUCH METHOD WHEREIN THE BAR OF SOAP TO BE IRRADIATED CONTAINS A HIGH ENERGY ELECTRON COLOR-SENSITIVE DYE; AND THE FURTHER MODIFICATION OF SUCH METHOD WHEREIN THE DESIGN IS TAPERED THROUGH THE SHIELD TO ALLOW SUBSTANTIALLY ALL RADIATION PASSING INTO THE DESIGN TO EMERGE THERETHROUGH WITHOUT STRIKING THE RADIATION IMPENETRABLE MATERIAL OF THE SHIELD.

Jan. 19, 1971 MACH ETAL 3,556,964

ELECTRON IRRADIATION PROCESS Filed July 19, 1967 2 Shcets-Sh0et 1 5? Hj'AHw ni THOMAS E MA c/l 3 2 4 :5/ 0A v10 7485/ WIN VIII/Illa .ToH/v R 0MFA RA Jan. 19, 1971 T. MACH ET AL ELECTRON IRRADIATION PROCESS FiledJuly 19, 1967 ELECTRON BEAM IE- (V8035 8N RE L14 7'/ V5 /0N/ZA 770/VSOAP BAR REL/4 771 5 2 Sheets-Sheet 2 ELECTRON BEAM wgw WW/? SOAP BARCH=CH I CH3 /00 Q 60 Q 60 g .40 S/DE/ (GR/1M5 PER CM /Mev.)

INVEN'IORS THOMAS Ff vncfl DA V/D TABER JOHIV/ OWEARA BYQ P/VEY UnitedStates Patent 3,556,964 ELECTRON IRRADIATION PROCESS Thomas F. Mach,Chicago, and David Taber, Evanston, Ill., and John P. OMeara, Orinda,Califi, assignors to Armour and Company, Chicago, 11]., a corporation ofDelaware Filed July 19, 1967, Ser. No. 654,566

Int. Cl. B01j 1/10 U.S. Cl. 204-158 ABSTRACT OF THE DISCLOSURE A methodfor producing a multiple-color soap bar by directing high energyelectrons toward a surface of a soap bar, interpositioning, between thebar surface and the electron source, a shield having a design therein,and causing the design configuration to be applied to the soap bar bycoloration or a change in color of the portion of the bar exposed to theelectron radiation; and the modification of such method wherein the barof soap to be irradiated contains a high energy electron color-sensitivedye; and the further modification of such method wherein the design istapered through the shield to allow substantially all radiation passinginto the design to emerge therethrough without striking the radiationimpenetrable material of the shield.

BACKGROUND OF THE INVENTION A This invention relates to a process forproducing a multiple colored bar of soap or other like material. Moreparticularly it relates to utilizing high energy electrons to produce acolor change in a dye-containing colored bar of soap.

Dyes known to be sensitive to radiation have generally been used toindicate the presence of sterilizing atomic radiation, viz they havebeen used in water solutions or in printing inks absorbed upon materialsfor use as radiation dosimeters. Radiation-sensitive dyes have also beenused for imprinting symbols upon light-sensitive data recordingmaterials (U.S. Pat. No. 2,953,454).

For many years the soap industry and others have been interested inpermanently identifying soap bars--that is,

they have been interested in being able to link a bar of soap by meansof an indicia to its brand or source after the consumer has purchasedthe bar and put it into usage. The present practice is to cut an indiciaupon the surface of the bar penetrating only a fraction of an inch intothe bar. Once this bar has been put into use, the outer soap is worn offthe bar and the indicia is obliterated.

Many techniques have been explored in the eifort to permanently identifya soap bar. One known technique involves forming an aperture in a soapbar and introducing a distinctive soap insert into the aperture (U.S.Pat. No. 2,423,435). This technique and other methods for mechanicallymeshing two separate different-colored soaps have not proved entirelysatisfactory due to difficulties in merging the two soaps into acompleted bar, keeping the inserted soap from coming out of the bar andthe commercial impracticality of purchasing or making costly and complexadditional machinery.

SUMMARY OF THE INVENTION We have discovered that high energy electronradiation will induce a change in color or a fading or bleaching incolor of commercially available colored soap bars.

13 Claims 3,556,964 Patented Jan. 19, 1971 ice maintained in the bar fora long period of time. In addition, we have discovered that a moresharply defined color contrast may be produced in the soap bar throughthe use of a radiation shield having a tapered design cut-out.

Therefore, it is an object of this invention to temporarily identify abar of soap for purposes of determining retail sales turnover, tagging aproduction run, and the like.

It is also an object of this invention to provide a process forpermanently identifying a bar of soap.

It is another object of this invention to provide a proc ess forproducing a soap bar having a distinctive indicia.

Another object of this invention is to provide a process for producing,in a few simple additional steps, a bar of soap having a distinctiveindicia imprinted in depth therein so as to be visible throughout longusage of the soap bar.

Still another object of this invention is to provide a process forproducing an indicia bar of soap containing an electronradiation-sensitive dye and having a sharply defined indicia which willbe clearly visible throughout the useful life of the soap bar.

A further object of this invention is to provide novel soap bars havinga distinctive indicia produced by exposure to high energy electronradiation, which indicia is permeated throughout the bar so as to bevisible even after portions of the bar have been worn away throughwashings with this bar.

Other objects and advantages and a further understanding of the presentinvention will become more apparent from the ensuing description andexamples, taken in conjunction with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents a schematic view ofa batchwise, trayby-tray process for irradiating soap bars with highenergy electrons.

FIG. 2 is a perspective view of the indicia bar.

FIG. 3 is a cross sectional view of the indicia bar of FIG. 2 takenalong line 33.

FIG. 4 is a top view showing one type of radiation shield which can beused in the irradiation process illustrated in FIG. 1.

FIG. 4A is a partial cross-section taken along line 4A-4A of FIG. 4.

FIG. 5 is a top view showing another type of radiation shield which canbe used in the tray-by-tray irradiation process illustrated in FIG. 1.

FIG. 5A is a partial cross-section taken along line 5A5A of FIG. 5.

FIG. 6 is a partial cross-section of one type of radia- DESCRIPTION OFTHE PREFERRED EMBODIMENTS In a specific embodiment, our invention may beexemplified by incorporating an effective amount of a hereinafterdescribed radiation-sensitive dye or dye mixture which undergoespermanent color change upon irradiation into a bar of soap or other likematerial; directing high energy electron radiation toward a surface ofthe bar; in-

terpositioning between that surface of the bar and the source of theradiation a radiation shield having a design to be applied to the bar bya change in color of the surface portion of the bar exposed to theradiation passing through a portion of the shield.

As herein used the term indicia shall mean one or more symbols, figures,letters, trademarks, designs, patterns and the like identifyingcharacters. The terms twocolored and diiferently colored, as used todescribe the color difference between the indicia portion and theremaining or background portion of the indicia soap bar, shall mean andrefer to different colors or different shades of color for the indiciawith respect to the color of the soap bar.

The term soap refers to the water-soluble ammonium, metallic, organicbase salts of various fatty acids, such as soya, coconut oil and tallowwhich are chiefly lauric, myristic, oleic, palmitic and stearic acids.As used in this specification and claims, the terms soap and soap barare intended to cover products in which soap is a substantialconstituent, for example, bar, cake, flake and granular soaps;toothpaste; cleansing creams, and the like.

High energy electrons--that is electrons shot in a 'beam from anaccelerator-have approximately a million times the energy of a typicalchemical bond and about one hundred thousand times the energy requiredto ionize molecules. The energy of the beam of such electrons ismeasured in million electron-volts (mev.), where one rmev. is defined asthe energy carried by an electron accelerated across a voltagedifference of one million volts. High energy electrons can causeelectrical changes in substances such as dyes by ionizing and excitingmolecules resulting in chemical-physical changes in the substance, suchas a color change of the dye. The intensity of color change at any givendepth of penetration for a given dye and soap system will be generallydependent upon the radiation dosage; and the depth of penetration of thecolor change into the soap bar will be generally dependent upon theelectron beam energy.

Radiation dosage, measured in megarads (mrad) or millions of rads, is afunction of the number of electrons impinging upon the substance beingirradiated and the amount of energy lost per unit length of electrontravel through the substance. One rad is 624x million electron volts pergram. The electron beam energy, measured in millions of electron volts(mev.), is a function of the accelerating potential through which theelectrons pass 'before emerging from an accelerator as a high energyelectron beam.

Referring to the drawings, our novel electron radiationimprinted indiciasoap bar is shown in perspective view in FIG. 2. The bar has an indicia21 color-distinctive with respect to the remaining portion 23 of thebar. Such indicia 21 may be of any desired configuration and may be ofeither a different color or a different shade of color from theremaining portion 23. FIG. 3 is a cross section of the same soap barillustrating the depth of the penetration of indicia 21 into the bar.Penetration of indicia 21 through about one-half of the soap bar, asdefined by the solid line 22, will generally occur with single-side 3-6mev. and 2-5 mrad irradiation of a bar of soap about 1% inches thick.Using thinner bars of soap or increased electron beam energy and dosagewill cause the indicia to be imprinted throughout the depth of the bar,as illustrated by dotted lines 24 of FIG. 3. Full penetration of theindicia may also be achieved by irradiating the bar from both sidesthatis, by double-bombardment of the bar. The same electron beam energy anddosage that will cause indicia 21 to penetrate about half-way throughthe 'bar on single-side irradiation, as illustrated in FIG. 3, willelfect on double bombardment (from each side) an indicia 21 penetratingthrough the entire bar.

Either single bars or a plurality of bars, such as a tray of bars, maybe irradiated. Rapid irradiation of the bars may be by either acontinuous operation or a batch operation. FIG. 1 schematicallyillustrates a tray-by-tray batch operation wherein a number of soap bars11 are placed into tray 12, and shield 10 is then placed over the bars11. By means of conveyor 13, the trays 12 are passed under a high energyelectron beam source 9 so as to expose portions of the bars 11 to apredetermined electron beam energy and dose to result in indicia bars22.

Shield 10 of FIG. 1, made of lead, brass, steel or other materialimpenetrable by the radiation, may be either of two types depending onwhether only the indicia 21 portion of the indicia soap bar is to beirradiated or whether the background area 23 is to be irradiated.

To irradiate the background area 23 while shielding indicia area 21 ofthe soap bar, a male shield, FIG. 5, is used. This shield is formed ofany radiation penetrable material 51, such as a sheet of rubber latex,onto which is fastened a number of radiation impenetrable designs 53, asshown in FIG. 5A. These designs are formed from lead or any otherradiation impenetrable material.

Another type of shield is shown in FIG. 4. This is a female shield andconsists of a sheet of lead 41 or any other radiation impenetrablematerial. A series of designs 43 are cut through or into sheet 41 so asto allow the radiation to pass through design 43, as illustrated in FIG.4A. As shown in FIG. 6, design 43 of sheet 41 may be cut through sheet43 so that walls 61 are substantially parallel to each other andperpendicular to upper surface 62 and lower surface 62 of design 43.

As shown in FIG. 6, when the penetrating radiation comes from anelectron beam source in a. spread beam, such as occurs when an indirectelectron accelerator is utilized or when a number of bars are to beirradiated simultaneously, a certain amount of radiation passing throughthe design 43 will penetrate through the walls 61 and the lower surface64 of the shield. Such radiation, although partially blocked by theradiation impenetrable material of the shield, may be sufiicient tocause a lessened or partial color change of the soap bar color at area64 of FIG. 6. Thereby the full radiation color change elfect produced atarea 62 of FIG. 6 may be surrounded by a partial color change of adifferent shade or color at area 64. This partial color change effectcan be decreased or eliminated by tapering the aperture of the designthrough sheet 41 to conform the aperture to the path of the electronbeam, as illustrated in FIG. 7. For example, using an electron beamscanning an angle of 16, sharply defined indicia may be obtained bycausing walls 65 to angle 16 into sheet 41 as illustrated in FIG. 7.Thus the full electron beam passes through the design and penetratesinto the soap bar.

We have also found that incorporating certain dyes into the soap barprior to irradiation greatly increases the color contrast, clarity anddepth of penetration of the resulting indicia, and permits the use oflower electron beam energies and doses. Certain of these dyes whenincorporated intosoap cause a permanent color change of the irradiatedarea of the soap. Other dyes cause a color change of the irradiatedarea; but, upon aging of the bar, there is a gradual reversal of theradiation-induced color back toward its original non-irradiated color.

Azo dyes having a symmetrical arrangement of aromatic ring structuresabout the azo radical (N=N), as illustrated in FIGS. 8 and 9, exhibit arelatively irreversible color change upon incorporation into soap andirradiation. This irreversible effect will hereinafter be referred to asa stable color change. As an example of an azo dye exhibiting stablecolor change, External D&C

I Red No. 8 (Colour Index designation Acid Red 88) incorporated intosoap at a level of 0.01% by weight results in a rose colored soap barwhich undergoes, upon sufiicient irradiation, a stable change to a goldcolor. The structural configuration of External D&C Red No. 8 is set outin FIG. 8, showing its symmetrical ring arrangement. Another example ofan azo dye havinga symmetrical ring arrangement is D&C Black No. 1(Colour Index designation Acid Black 1), shown in FIG. 9. This dye whenincorporated into soap at a level of 0.01% results in dark blue coloredsoap which undergoes a stable color change to White upon sufiicientirradiation.

Another azo dye, FD&C Yellow No. 6, structurally illustrated in FIG. 10,does not have a symmetrical ring arrangement around the azo radical.This dye does not exhibit the above-described stable color change whenincorporated into soap and exposed to high energy electron irradiation;but exhibits a color change which gradually reverts back to itsnon-irradiated color. This reversibility can be minimized or arrested soas to achieve a stable radiation color change, by using a mixture ofsymmetrical and unsymmetrical azo dyes wherein at least 30% of the dyemixture is a symmetrical azo dye. For example, a dye mixture of 30%External D&C Red No. 8 and 70% FD&C Yellow No. 6 incorporated into soapat a concentration of 0.01% produces a stable color change uponradiation from red to yellow.

Still another dye, Genacryl Orange R (Colour Index designation BasicOrange R), exhibits stable color change when incorporated into soap andirradiated, in addition to FD&C Yellow No. 6, include: FD&C Blue No. 1;FD&C Blue No. 1 Lake; D&C Blue No. 1; D&C Red No. 5; D&C Red No. 19; D&CRed No. 31; D&C Green No. 5; D&C Yellow No. 1; D&C Orange No. 5;methylene blue; quinone; azobenzene; and 2,3,5-triphenyl-2,4-tetrazoliurn chloride.

The suitable dyes, both the color stable and the color reversible andcombination thereof may be added to the soap at any suitable step in themanufacture of the soap. We prefer to add the dye to the soapimmediately prior to the ploddin stage.

Relatively small amounts of the dyes are suificient to obtain theadvantages of this invention. Satisfactory results are obtained when thedye is present in a concentration of from 0.007% to 0.15% by weight onthe basis of the weight of the soap. A preferred range is generally aweight concentration of about 0.01% to about 0.1%, although this willvary depending on the specific dye used and the colors desired.Practical considerations such as intensity of the color of thenon-irradiated soap and cost factors limit the desirability of amountsmuch greater than 0.15%, although greater amounts can be used forgreater contrast when desired. Amounts less than 0.007% will producesome color change in certain instances, but generally the color contrastbetween the irradiated and the non-irradiated portions of the soap willbe less than is usually desired due to the lightness of the resultingsoap colors. Absorbing the dye on titanium dioxide before incorporatingit into the soap improves the intensity of the color change and theclarity of the indicia detail.

The intensity of radiation color change developed in any suitabledye-soap system is dependent on the radiation dose, measured inmegarads, and the penetration of the radiation into the soap bar dependson the electron beams energy, measured in mev. As a beam of electronspasses through a substance, the electrons are gradually slowed down. Asthe electrons slow down, they spend more time near each atom in thesubstance and thereby become more efficient at ionization. However thepenetrating ability of an electron beam is proportional to its energyand inversely proportional to the density of the product beingirradiated. Thus the beam energy theoretically required to penetrate anindicia half-way through a %-inch thick bar of soap having a density of1.020 grams/cc. is 2.1 mev. (as found by the Feather equation forcalculating penetration of cathode ray beams).

FIG. 12 illustrates dosage variation for this bar of soap. As shown inFIG. 12, the dose that will be delivered to the bar of soap is notuniform to this calculated depth because the radiation dosage deliveredto'the bar of soap will vary with the depth of penetration into the barfor any given beam energy level. The cross-hatched area labeled Side No.1 of FIG. 12 shows the variation of penetration obtainable withsingle-side irradiation. The area labeled Side No. 2 is a mirror imageof the singleside radiation penetrating from the other side, as will beobtained with double-bombardment. A preferred minimum energy to achieveoptimum dose half-way through this bar of soap is about 2.5 mev. Thisenergy level may be used to imprint an indicia throughout the entiredepth of this bar by irradiating the bar from both sides(doublebombardment combining the areas shown for Side 1 and Side 2).

Since dose and beam energy are.independent variables, a particular colorintensity and depth of penetration effect can be produced by a number ofbeam energy-dosage combinations. FIG. 13 illustrates graphically thedepth of penetration curves for some of the high energy electron beamlevels that are useful in our process. Also, at any particular depth ofpenetration (measured in centimeters in FIG. 13) the relative percent ofionization will be greater with a higher beam energy than with a lowerbeam energy. Increasing the dosage for a particular beam energy levelacts to overcome that beam energys lower percent ionization atparticular depth and will produce a color change effect equivalent to alower dosage of a higher beam energy.

For soap bars containing a dye other than the particularly desirablecolor stable or gradually reversible dyes of this invention, higherenergy and dosage equivalents are preferable. For example, it appearsthat about 9 mev. and a dose from about 4.0 to 7.0 mrad, or theequivalent thereof, is suitable for a %-inch soap bar to produce agradually reversible indicia. For a A-inch thick bar containing asuitable color reversible dye of this invention, about 6 mev. at a.dosage of 2 mrad is suitable. We have obtained desirable results for a%-inch thick soap bar containing 0.0125 of the stableradiation-bleaching dye External D&C Red No. 8 when irradiated at 3.0mev. and 4.0 mrad; an equivalent effect was achieved at 3.2 mev. at 3.0mrad (due to the depth-dose curve relationship illustrated in FIG. 3).Adsorbing this latter dye on titanium dioxide before incorporating thedye into the soap, and irradiating the bar by double-bombardment usingthe tapered female shield of FIG. 7 at 11 mev. and 6 mrad, resulted inan especially desirable indicia bar having a sharply defined distinctivewhite indicia imprinted with very little fuzzing of detail throughoutthe entire depth of the deep rose background bar.

In order to more fully describe this invention, the following specificexamples are provided but without in any way limiting the inventionthereto. In the specific examples hereinafter, the soap bars utilizedcontained about 15%-25% by weight sodium coco soap and 75% by weightsodium tallow soap. Reference in the following examples to a germicidalsoap means that a 50-50 mixture of 3,4,5 trichlorocarbanilide andhexachlorophene was added at a concentration of 1.5% by weight to thesoap.

Example I Bars of a germicidal soap, containing 0.00853% External D&CYellow No. 1 and 0.00078% FD&C Yellow No. 6 dyes to give the bars a goldcolor, were tested for color change and for etfect upon antibacterialproperties of the soap when irradiated with high energy electrons.

The bars were exposed to a 7 mrad dose at an electron beam energy of 3mev. using a Van de Graff accelerator. The entire bar was exposed,resulting in an irreversible color change from gold to tan-brown. Atlower doses, such color change did not occur in these bars.

T he irradiation did not appear to affect the antibacterial propertiesof the soap tested in vitro. Theresults of the tests; on antibacterialproperties showing minimum inhibition are-set forth in Table I.

thickness of 0.03 inch. The image on the surface of the irradiated barwas good, but the fine detail of the design configuration was lostwithin about inch penetration into the bar. Even when the 0.03 inchbrass base was milled out of the design, there was negligible improve-TABLE 1 5 4 ment. S'amws, gi a I )ouble layers of A inch thick leadsheets, through FDA 11229, which the letter K approximately 1 Inch highwith arms V inch thick was cut, were also used as shields. The Conrol-gold colored germici al soap 5 7.000 K was barel le ible at a de thof about /2 inch 'nto Test-irradiated gold colored germicidal soap. 57,000 10 y g p I the soap.

. TABLE II Color of bar prior to Radiation Color of Iirradiation/indicia dosage, indicia/ Appearance design mrad backgroundof indicia Depth of penetration Aqua:

Logotype'Design 2.0 White/Aqua--. Good- 5th section legible.

Do 0.4 do.. Letter K 2.0 Pink:

Logotype Design. 5.0 White/Pink Very faint." Letter K 5.0 do do. Gold:

n. 4. 0 White/Gold Extremely taint... 6.0 do Faint 4.0 do 6.0 do Fairlygood Example II Example III Using an Applied Radiation Corp. (ARCO)linear 3 sing the same equlpment, soap bars and operating accelerator,operated at an electron beam energy of approximately 11 mev., samples ofaqua, pink and gold colored germicidal soap bars weighing 4.99-5.11 oz.each and measuring 3 /2 x 2% x 1.13 inches were irradiated. The barscontained 0.0009% FD&C Blue Lake No. 1 and 0.0002% FD&C Yellow to givethem an aqua color; 0.0073%' FD&C Yellow No. 6 and 0.0002% Red No. 19 togive them a pink color; and 0.00853% External D&C Yellow No. l and0.00078% FD&C Yellow No. 6 to give them a gold color.

In this example, the design to be imposed by radiation color change ofthe soap was cut through either a brass or lead shield so that theelectrons passed through the design cut-out. The irradiated aqua soapbars were sectioned to determine the depth of color change and appearance of the indicia at each depth.

Table II shows the radiation dosages used, along with the observation ofthe appearance of the indicia. In all 0 conditions as set out in Example11, aqua, pink and gold germicidal soap bars were irradiated atapproximately 11 mev. using a male type of shield.

In this test the designs were cut from a A inch thick lead sheet andsecured to a rubber latex sheet so that the electrons could not passthrough the design, thus silhouetting the design against acolor-bleached background. The designs usedin this test were the lettersGK and HL, each letter approximately 1 inch high with arms /s inch wide,and the letter K approximately 1 inch high with arms inch wide.

The irradiated aqua bars were sectioned as set forth in Example 11 andthe results, as indicatedin Table III were superior to those obtained inExample II in that the non-irradiated-color design maintained reasonablecontrast and clarity to nearly one-half the depth of the soap change togive satisfactory contrast.

TABLE III Color of bar prior to Radiation Color of irradiation indieiadosage, indieia/ Appearance design mrad background of indicia Depth ofpenetration Aqua:

Letters GK 0. 4 White/Aqua... Good 5th *}52" section legible. ,LettersHL 0. 4 d Do.

Letter K 0.4 6th 052" section legible. D 0. 25

2.0 link:

Letters GK 0. 4 Not visible Do 1. 2 .do 3. O White/Pink- Very taint- 4.0do do G01 4. 0 White/ Gold .do Letters I IL 4.0 do do cases it wasnecessary to deliver a radiation dose of at least 2 mrad, using anelectron beam energy of 11 mev., to get satisfactory'colo'r contrast ofthe indicia into these bars. The aqua colored bars gave the best colorcontrast, although the color faded rapidly. The gold colored bars hadfairly good contrast at the higher radiation dosages; and the pinkcolored bars gave only a faint color contrast. 4

When the brass shield was used, a-% inch by 1 inch Example IV A numberof soap-dye systems were tested for color change, distinction of colorcontrast and color stability using 3.443.S6 02., 3 x 2 x 1.20 inch barsof soap without germicide and 3.58-3.70 02., 3 /2 x 2%; x 1.00

inch bars of soap with germicide exposed to an electron beam energy of 8mev. at a dose of 2 mrad from a linear accelerator.

In these tests, the soap bars containing dyes, were crown design wasfirst milled thereinto to a final brass placed in 12%; x 12% inchaluminum trays /s inch thick 10 and having sidewalls 1% inches high.Either alead or steel of the color distinction between the indicia andthe soap shield was placed over the tray and the tray was passedbackground. The faded circle observed immediately after under the beamof a linear accelerator to expose a porirradiation in certain test barscan primarily be attributed tion of each bar to an electron beam energyof 8 mev. to the effect of the electron beam penetrating through at adose of either 0.6 mrad, 2 mrad or 3 mrad. The part of the fringe areaof the shield around the unshields used were of the female typeconsisting of a 12 5 tapered design cut-out. inch by 18 inch sheet ofeither /2 inch thick lead or The effects of increasing the dose to 3mrad and deinch steel through which 1 x A inch crown-shaped de creasingthe close to 0.6 mrad are not indicated in the signs and 1 inch diametercircles had been cut through tables; but it was observed that for thissize bar of soap, without tapering, such as is shown inFIG. 6. the 3.0mrad dose level resulted in a sharper color con- The results of thesetests are set forth in Tables IV-A, trast than occurred with the 0.6mrad level. At the lower IV-B and IV-C. Table IV-A reports on germicidesoap dose level the circle indicia expanded from inch on bars whereasthe bars listed in Table IV-B did not contain one face of the bars toabout 1 /8 inches on the outer face added germicides. Table IV-C reportson the effects of of the bar. At the higher dose level, the circleindicia varying the dosage. expanded from inch to about 1% inches on theother TABLE IVA.GER1\IICIDAL SOAP, DYE SYSTEMS WITH REVERSIBLE COLORBLEACHING Percent dye I I I (based on Color and stability of indiciaweight of Dye added soap pellets) 1 hour v I v I 1 Week 1 monthGermicidal soap without any dye Colorless background, sl. yellow indiciaFaded FD&O Blue Lake No. 1 and FD&C Yellow N o. 6.-.. 0.0009 and 00002..Aqua, white Fading gray.-- Faded. Methylene Blue 0.01 Sl. faded green-.Fade 0.1 N HCl and Methylene Blue Blue, white indicia Do. 0.50% of NaOHand Methylene Blue 0 Do. 0.1 N H01 and 98% FD&C Blue No. 1 Lake and 2%Do.

FDdzO Yellow No. 6. 0.50% of 30% NaOH and 98% FD&C Blue No. 1 and 0.0103..do do..... Do.

2% FD&C Yellow No. 6.

TABLE IV-Br-NON-GERMICIDAL SOAP, DYE SYSTEMS WITH REVERSIBLE COLORBLEACHING Percent dye (based on Color and stability of indicia weight ofsoap Dye added pellets) 1 hour 1 week 1 month D&C Red No. 19 0.010 Pinkbackground, white indicia Light pink...- Faded. Azobenzene 0.025. Tan,white indicia Fading Do. D&C Green No. 5. 0.010- Blue-green, light greenindicia.. o Do. D&C Blue No. 1 0.010 Blue, white indicia Light green..-S1 fading D&C Yellow No. 1 0.010.-- Gold, pale yellow indicia Fade D&CYellow No. 6 0.010 Yellow, tan indicia White, light brown.

25% FD&O Blue No. 1 Lake and 75% FDdzC Red No. 19... 0.0125 Violet,faint pink indicia do Do.

% Methylene Blue and 50% FDiSzC Yellow No. 6 0.0125 Dark bluebackground, gray indicia-.. Light blue.... Do.

50% Methylene Blue and 50% D&C Red No. 19 0.0125 Blue, white indiciasurrounded by 1/16 do Do.

in. pink circle.

98% FDdzC Blue No. 1 Lake and 2% FD&C Yellow No. 6.. 0.0130 Blue, whiteindicia Faint white-.. Faded.

50% FD&C Blue No. 1 and 50% D&C Red No. 29 0.0125 Scarlet, white indiciaFaint Fading.

50% D&C Blue No. 1 and 50% D&C Red No. 19 00125---. Deep violet, whitetndieia... Pink Do.

22.5% D&C Red No. 19 and 77.5% FD&C Yellow No. 6---- 0.0125 Mild pinkwhite indicia Faint pink-. Faded.

22.5% FDdzC Red No. 2 Lake and 77.5% FD&C Yellow No. 0.0125Yellow-orange, white indicia Fading Do.

FD&C Red No. 2 Lake FD&C Yellow No. 6 and D&C Red 0.0075, 0.0030 Pinkbackground, white indicia .d0 Do.

No. 19. and 0.0032. 2,3,s-triphenyl-2,4tetrazo1i1un chloride 0.0125Light yellow, very white indicia sur- Cream, pink Color mostly roundedby in. pink ring. ring still pink and visible. only faintly visible.

TABLE side of the bar. Also the rate of fading was less at the [Effectsof varying dosage at 11 mev. for 1 inch thick germicidal soap high6rdose than at tha lower dosecontaining 0.0125% (basis: wt. of soap) ofExternal D&C Red No. 8]

Size of indicia on Example V Upper Lower 1 External D&C Red No. 8 dyewas added to nongermi- Soap Soap 9 9 cide containing soap pellets andthe soap bars formed Dosage, face, face, indicia] Design inch inchbackground therefrom were exposed to an electron beam energy of CircleWinch) 0 6 8 mev. at a dosage of 2 mrad from a linear accelerator 8 1using the procedure set forth in Example 'IV. The results 0 are setforth in Table V. g

Y The results show External D&C Red No. 8 underwent The dyes reported inTables IV-A and IV B generally stable color change from a rose to a goldcolor at this evidenced a gradual color reversibility-that is, withinexposure, even when the concentration of this dye was a month theradiation induced color reverted back tocut in half by the addition ofthe generally reversible dye ward the non-irradiated color, therebyresulting in a loss FD&C Yellow No. 6. In addition, the color changeapl1 peared stable under 72 hours constant exposure to white fluorescentlight and daylight.

an azo dye having a symmetrical arrangement of aromatic ring structureaboutthe azo'radical.

TABLE V Percent Color and stability of indieia dye in Dye v soap 1 houra1 week 1 month External D&C Red No. 8. L 0125 Rose background, gold'indicia Stable Stable no fading. 50% External D&C Red No.;8 and 50%FDdzC Yellow No. 6 0.01904 Pink, yellow indicia do, Do. 50% Extenal D&CRed N 8 and 50% D&QOrange No. 4 0. 0125 Orange-red, gold indioia do Do.

Example VI A series of 3.58-3.70 02., 3 x 2% x 1 inch soap barscontaining germicide and various dyes were irradiated and tested forcolor change and color stability.

The procedure used was that set forth in Example IV, exceptthat the barswere exposed to an electron beam energy of 11 mev. ,The exposed barsreceived a radiation dosage of 2.0 and 6.0 mrad. The entire bar wasexposed to electron radiation without shielding, so no indicia resulted.

The results are set forth in Table VI. The section of Table IV headed Acontains results at the lower radiation dosage and the Section Bcontains results at the.

higher dosage.

It was observed that adsorption of the External D&C Red No. 8 dye uponTiO caused a more intense color change upon irradiation withoutaifecting color stability.

The effect of using D&C Black No. 1 as the test dye and exposing the barto 11 mev. at 6.0 mrad was to produce a radiation color changed indiciawhich did not fade or tend to revert in color after one months storage.This stable color change was not affected by exposing the irradiated barto 72 hours of white fluorescent light and daylight.

4. The method of claim 1 in which said soap contains a mixture of azodyes wherein at least about 30% by weight of said mixture is an azo dyehaving a symmetrical arrangement of aromatic ring structures about theazo radical.

positioning between said bar and the source of the radiation a means fordirecting the radiation to a predetermined portion of the bar therebycausing a change in color of said predetermined portion of said bar.

'7. The method of claim 6 in which said radiationsensitive dye ispresent in an amount of at least 0.05%

by weight of said bar.

8. The method of claim 6 in which said dye is an azo dye having asymmetrical arrangement of aromatic ring structure about the azoradical.

TABLE VL-GERMICIDAL SOAP-DYE SYSTEMS INDICATING REVERSIBLE ANDIRREVERSIBLE COLOR CHAN GES WITHOUT INDICIA PRINTING Percent PercentColor and stability dye in Dye soap 1 hour 1 month 1 week (A) At2.0megarad dosage: v

2,3,5-triph enyltetrazolium chloride 0. 0125 0. 0125 0. 0125 0.0125 0.0125 (B) At 6.0 megarad dosage:

White White White, stable.

D&C Black No. 1 0.0125 D&C Red No. 31 0.0125 Yellow- Yellow Fading.External D&C Red No. 8 adsorbed on TiOz- 0. 0125 Tan Tan; Tan, stable.Triphenylphosphino silver nitrate 0. 0125 Faint yellow 0. 0125 Faintcream S1. fading-.. Fading.

External D&C Yellow No. 1

Same stability as without TiOa but has deeper color.

2 Bar discoloring.

While the present invention has been described an exemplified withrespect to certain embodiments, it is not so limited; and it is to beunderstood that variations and modifications thereof, obvious to thoseskilled in the art, may be'rnade without parting from the spirit andscope of ourinv'ention.

We claim: i

1. A method of inducing a color change in a bar of soap selected fromthe group consisting of the watersoluble ammonium, metallic, and organicbase salts of various'fatty acids by irradiating at least a portion ofsaid bar with high energy electrons. I

2. The method of claim 1 in which said soap contains adye.

3. The method of claim 1 in which said soap contains 9. The method ofclaim 6 in which said dye is a mixture of azo dyes containing at leastabout 30% of an azo dye having a symmetrical arrangement of aromaticring structure about the azo radical.

10. The method of claim 6 in which said dye is an azo dye selected fromthe group consisting of External D&C Red No. 8, D&C Black No. 1, andGenacryl Orange R.

11. The method of claim 6 in which said means comprises a sheet ofelectron radiation penetrable material having affixed thereto anindicia, said indicia being impenetrable by: high energy radiation so asto cause the configuration of the indicia to be applied to the bar ofthrough said shield.

12. The method of claim 6 in which said means comprises a sheet ofelectron radiation impenetrable material having an indicia aperture cutthereinto, said indicia being penetrable by at least a portion of saidhigh energy electron radiation so as to cause the configuration of theindicia to be applied to the bar of soap by exposure of a portion of thebar to the radiation through said indicia.

13. The method of claim 12 in which said indicia aperture is taperedthrough the shield to substantially conform the aperture to the path ofthe high energy electron radiation.

1 4 References Cited UNITED STATES PATENTS OTHER REFERENCES Landau:Chemistry & Industry (Mar. 31, 1962), pp.

10 HOWARD S. WILLIAMS, Primary Examiner

